linux-kernel - [PATCH 3.12 60/78] usb: gadget: f_midi: Fixed a bug when buflen was smaller than wMaxPacketSize

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Message-Id: <7d4647a410edf0b85529188ac364f365b5a3c7fb.1461323133.git.jslaby@suse.cz>
Date:	Fri, 22 Apr 2016 13:05:43 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	"Felipe F. Tonello" <eu@...ipetonello.com>,
	Felipe Balbi <felipe.balbi@...ux.intel.com>,
	Oliver Neukum <oliver@...kum.org>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 60/78] usb: gadget: f_midi: Fixed a bug when buflen was smaller than wMaxPacketSize

From: "Felipe F. Tonello" <eu@...ipetonello.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 03d27ade4941076b34c823d63d91dc895731a595 upstream.

buflen by default (256) is smaller than wMaxPacketSize (512) in high-speed
devices.

That caused the OUT endpoint to freeze if the host send any data packet of
length greater than 256 bytes.

This is an example dump of what happended on that enpoint:
HOST:   [DATA][Length=260][...]
DEVICE: [NAK]
HOST:   [PING]
DEVICE: [NAK]
HOST:   [PING]
DEVICE: [NAK]
...
HOST:   [PING]
DEVICE: [NAK]

This patch fixes this problem by setting the minimum usb_request's buffer size
for the OUT endpoint as its wMaxPacketSize.

Acked-by: Michal Nazarewicz <mina86@...a86.com>
Signed-off-by: Felipe F. Tonello <eu@...ipetonello.com>
Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
Cc: Oliver Neukum <oliver@...kum.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/usb/gadget/f_midi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/f_midi.c b/drivers/usb/gadget/f_midi.c
index 263e721c2694..e7f1b967a5bb 100644
--- a/drivers/usb/gadget/f_midi.c
+++ b/drivers/usb/gadget/f_midi.c
@@ -365,7 +365,9 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 	/* allocate a bunch of read buffers and queue them all at once. */
 	for (i = 0; i < midi->qlen && err == 0; i++) {
 		struct usb_request *req =
-			alloc_ep_req(midi->out_ep, midi->buflen);
+			alloc_ep_req(midi->out_ep,
+				max_t(unsigned, midi->buflen,
+					bulk_out_desc.wMaxPacketSize));
 		if (req == NULL)
 			return -ENOMEM;
 
-- 
2.8.1